Log wood + pellet bivalence: securing autonomy for a rural project in Luxembourg

Why combine logs and pellets on the same project?

A bivalent boiler accepts two fuels on the same body: logs as a manual backup, pellets in automatic mode. This architecture covers supply gaps, price spikes and homeowner absences.

On a rural project in Luxembourg, bivalence halves the supply risk and smooths the heating bill, as pellet and gas prices can swing 20 to 30% from one season to the next.

What does the technical regulation require?

Any new biomass boiler must meet EcoDesign EU 2015/1189 and EN 303-5 Class 5: these are the two items that validate the permit file and unlock the 2026 Klimabonus.

For pellets, require ENplus A1 certification: it guarantees stable calorific value, low ash content and clean auger dosing.

• EcoDesign EU 2015/1189: minimum emissions and efficiency, mandatory.
• EN 303-5 Class 5: required by the Luxembourg administration.
• ENplus A1: pellet quality to mention in the specifications.

How much does the 2026 Klimabonus actually pay for a bivalent system?

In Luxembourg, only the pellet side of a bivalent system is eligible: up to €8,000 for a single-family home, provided an old installation is replaced. Without replacement, the cap drops to €4,000.

A buffer tank triggers a +15% bonus. Pairing the boiler with solar thermal adds a flat €1,000. Municipal grants, variable by commune, stack with the state aid: use the Klima-Agence simulator to size the real amount for your project.

• Single-family home: up to €8,000 (with replacement) / €4,000 (without).
• Multi-family building: €6,000 per unit, capped at €40,000.
• District heating: €6,000, capped at €24,000.
• Buffer tank bonus: +15%. Solar thermal bonus: +€1,000.

What must be planned at the sketch stage to avoid redesign?

Three volumes to fix in the plan: the boiler room (≥ 6 m², direct delivery access), the pellet silo (2-3 m³ for 150 m², roughly 1.5-2 t per year) and the log storage (dry, ventilated, within 5 m of the firebox).

On the hydraulic side, plan a buffer tank ≥ 500 L, a mixing valve and room for a possible solar thermal connection: this triggers both 2026 Klimabonus bonuses and lifts resale value.

• Pellet silo: 2-3 m³, fill hatch accessible to the blower truck.
• Buffer tank: ≥ 500 L, solar connection pre-plumbed.
• Boiler room: fire-rated door, high and low ventilation, sealed floor.